1//===- CFG.h - Process LLVM structures as graphs ----------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines specializations of GraphTraits that allow Function and
11// BasicBlock graphs to be treated as proper graphs for generic algorithms.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_IR_CFG_H
16#define LLVM_IR_CFG_H
17
18#include "llvm/ADT/GraphTraits.h"
19#include "llvm/ADT/iterator.h"
20#include "llvm/ADT/iterator_range.h"
21#include "llvm/IR/BasicBlock.h"
22#include "llvm/IR/Function.h"
23#include "llvm/IR/InstrTypes.h"
24#include "llvm/IR/Value.h"
25#include "llvm/Support/Casting.h"
26#include "llvm/Support/type_traits.h"
27#include <cassert>
28#include <cstddef>
29#include <iterator>
30
31namespace llvm {
32
33//===----------------------------------------------------------------------===//
34// BasicBlock pred_iterator definition
35//===----------------------------------------------------------------------===//
36
37template <class Ptr, class USE_iterator> // Predecessor Iterator
38class PredIterator : public std::iterator<std::forward_iterator_tag,
39                                          Ptr, ptrdiff_t, Ptr*, Ptr*> {
40  using super =
41      std::iterator<std::forward_iterator_tag, Ptr, ptrdiff_t, Ptr*, Ptr*>;
42  using Self = PredIterator<Ptr, USE_iterator>;
43  USE_iterator It;
44
45  inline void advancePastNonTerminators() {
46    // Loop to ignore non-terminator uses (for example BlockAddresses).
47    while (!It.atEnd() && !isa<TerminatorInst>(*It))
48      ++It;
49  }
50
51public:
52  using pointer = typename super::pointer;
53  using reference = typename super::reference;
54
55  PredIterator() = default;
56  explicit inline PredIterator(Ptr *bb) : It(bb->user_begin()) {
57    advancePastNonTerminators();
58  }
59  inline PredIterator(Ptr *bb, bool) : It(bb->user_end()) {}
60
61  inline bool operator==(const Self& x) const { return It == x.It; }
62  inline bool operator!=(const Self& x) const { return !operator==(x); }
63
64  inline reference operator*() const {
65    assert(!It.atEnd() && "pred_iterator out of range!");
66    return cast<TerminatorInst>(*It)->getParent();
67  }
68  inline pointer *operator->() const { return &operator*(); }
69
70  inline Self& operator++() {   // Preincrement
71    assert(!It.atEnd() && "pred_iterator out of range!");
72    ++It; advancePastNonTerminators();
73    return *this;
74  }
75
76  inline Self operator++(int) { // Postincrement
77    Self tmp = *this; ++*this; return tmp;
78  }
79
80  /// getOperandNo - Return the operand number in the predecessor's
81  /// terminator of the successor.
82  unsigned getOperandNo() const {
83    return It.getOperandNo();
84  }
85
86  /// getUse - Return the operand Use in the predecessor's terminator
87  /// of the successor.
88  Use &getUse() const {
89    return It.getUse();
90  }
91};
92
93using pred_iterator = PredIterator<BasicBlock, Value::user_iterator>;
94using const_pred_iterator =
95    PredIterator<const BasicBlock, Value::const_user_iterator>;
96using pred_range = iterator_range<pred_iterator>;
97using pred_const_range = iterator_range<const_pred_iterator>;
98
99inline pred_iterator pred_begin(BasicBlock *BB) { return pred_iterator(BB); }
100inline const_pred_iterator pred_begin(const BasicBlock *BB) {
101  return const_pred_iterator(BB);
102}
103inline pred_iterator pred_end(BasicBlock *BB) { return pred_iterator(BB, true);}
104inline const_pred_iterator pred_end(const BasicBlock *BB) {
105  return const_pred_iterator(BB, true);
106}
107inline bool pred_empty(const BasicBlock *BB) {
108  return pred_begin(BB) == pred_end(BB);
109}
110inline pred_range predecessors(BasicBlock *BB) {
111  return pred_range(pred_begin(BB), pred_end(BB));
112}
113inline pred_const_range predecessors(const BasicBlock *BB) {
114  return pred_const_range(pred_begin(BB), pred_end(BB));
115}
116
117//===----------------------------------------------------------------------===//
118// BasicBlock succ_iterator helpers
119//===----------------------------------------------------------------------===//
120
121using succ_iterator =
122    TerminatorInst::SuccIterator<TerminatorInst *, BasicBlock>;
123using succ_const_iterator =
124    TerminatorInst::SuccIterator<const TerminatorInst *, const BasicBlock>;
125using succ_range = iterator_range<succ_iterator>;
126using succ_const_range = iterator_range<succ_const_iterator>;
127
128inline succ_iterator succ_begin(BasicBlock *BB) {
129  return succ_iterator(BB->getTerminator());
130}
131inline succ_const_iterator succ_begin(const BasicBlock *BB) {
132  return succ_const_iterator(BB->getTerminator());
133}
134inline succ_iterator succ_end(BasicBlock *BB) {
135  return succ_iterator(BB->getTerminator(), true);
136}
137inline succ_const_iterator succ_end(const BasicBlock *BB) {
138  return succ_const_iterator(BB->getTerminator(), true);
139}
140inline bool succ_empty(const BasicBlock *BB) {
141  return succ_begin(BB) == succ_end(BB);
142}
143inline succ_range successors(BasicBlock *BB) {
144  return succ_range(succ_begin(BB), succ_end(BB));
145}
146inline succ_const_range successors(const BasicBlock *BB) {
147  return succ_const_range(succ_begin(BB), succ_end(BB));
148}
149
150template <typename T, typename U>
151struct isPodLike<TerminatorInst::SuccIterator<T, U>> {
152  static const bool value = isPodLike<T>::value;
153};
154
155//===--------------------------------------------------------------------===//
156// GraphTraits specializations for basic block graphs (CFGs)
157//===--------------------------------------------------------------------===//
158
159// Provide specializations of GraphTraits to be able to treat a function as a
160// graph of basic blocks...
161
162template <> struct GraphTraits<BasicBlock*> {
163  using NodeRef = BasicBlock *;
164  using ChildIteratorType = succ_iterator;
165
166  static NodeRef getEntryNode(BasicBlock *BB) { return BB; }
167  static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); }
168  static ChildIteratorType child_end(NodeRef N) { return succ_end(N); }
169};
170
171template <> struct GraphTraits<const BasicBlock*> {
172  using NodeRef = const BasicBlock *;
173  using ChildIteratorType = succ_const_iterator;
174
175  static NodeRef getEntryNode(const BasicBlock *BB) { return BB; }
176
177  static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); }
178  static ChildIteratorType child_end(NodeRef N) { return succ_end(N); }
179};
180
181// Provide specializations of GraphTraits to be able to treat a function as a
182// graph of basic blocks... and to walk it in inverse order.  Inverse order for
183// a function is considered to be when traversing the predecessor edges of a BB
184// instead of the successor edges.
185//
186template <> struct GraphTraits<Inverse<BasicBlock*>> {
187  using NodeRef = BasicBlock *;
188  using ChildIteratorType = pred_iterator;
189
190  static NodeRef getEntryNode(Inverse<BasicBlock *> G) { return G.Graph; }
191  static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); }
192  static ChildIteratorType child_end(NodeRef N) { return pred_end(N); }
193};
194
195template <> struct GraphTraits<Inverse<const BasicBlock*>> {
196  using NodeRef = const BasicBlock *;
197  using ChildIteratorType = const_pred_iterator;
198
199  static NodeRef getEntryNode(Inverse<const BasicBlock *> G) { return G.Graph; }
200  static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); }
201  static ChildIteratorType child_end(NodeRef N) { return pred_end(N); }
202};
203
204//===--------------------------------------------------------------------===//
205// GraphTraits specializations for function basic block graphs (CFGs)
206//===--------------------------------------------------------------------===//
207
208// Provide specializations of GraphTraits to be able to treat a function as a
209// graph of basic blocks... these are the same as the basic block iterators,
210// except that the root node is implicitly the first node of the function.
211//
212template <> struct GraphTraits<Function*> : public GraphTraits<BasicBlock*> {
213  static NodeRef getEntryNode(Function *F) { return &F->getEntryBlock(); }
214
215  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
216  using nodes_iterator = pointer_iterator<Function::iterator>;
217
218  static nodes_iterator nodes_begin(Function *F) {
219    return nodes_iterator(F->begin());
220  }
221
222  static nodes_iterator nodes_end(Function *F) {
223    return nodes_iterator(F->end());
224  }
225
226  static size_t size(Function *F) { return F->size(); }
227};
228template <> struct GraphTraits<const Function*> :
229  public GraphTraits<const BasicBlock*> {
230  static NodeRef getEntryNode(const Function *F) { return &F->getEntryBlock(); }
231
232  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
233  using nodes_iterator = pointer_iterator<Function::const_iterator>;
234
235  static nodes_iterator nodes_begin(const Function *F) {
236    return nodes_iterator(F->begin());
237  }
238
239  static nodes_iterator nodes_end(const Function *F) {
240    return nodes_iterator(F->end());
241  }
242
243  static size_t size(const Function *F) { return F->size(); }
244};
245
246// Provide specializations of GraphTraits to be able to treat a function as a
247// graph of basic blocks... and to walk it in inverse order.  Inverse order for
248// a function is considered to be when traversing the predecessor edges of a BB
249// instead of the successor edges.
250//
251template <> struct GraphTraits<Inverse<Function*>> :
252  public GraphTraits<Inverse<BasicBlock*>> {
253  static NodeRef getEntryNode(Inverse<Function *> G) {
254    return &G.Graph->getEntryBlock();
255  }
256};
257template <> struct GraphTraits<Inverse<const Function*>> :
258  public GraphTraits<Inverse<const BasicBlock*>> {
259  static NodeRef getEntryNode(Inverse<const Function *> G) {
260    return &G.Graph->getEntryBlock();
261  }
262};
263
264} // end namespace llvm
265
266#endif // LLVM_IR_CFG_H
267